A form managing system for reading a paper form with an image scanner device, for putting the paper form image into an electronic document, and for saving the obtained form image data as trail information is known. In such a form managing system, the capacity of storage for saving form image data becomes huge, leading to an increase in system cost and complexity of system operations. Accordingly, the amount of form image data saved in a storage device needs to be reduced. In the meantime, an image quality of a level available as trail information is needed for an image of an original form reproduced from saved form image data.
The amount of form image data is reduced by being compressed with a still image compression technique such as a JPEG (Joint Photographic Experts Group) method. However, it is a serious problem that a storage capacity of recent form managing systems has become huge, and a data compression rate that can be obtained by applying a still image compression technique is not fully effective as measures against this problem under present circumstances.
In the meantime, as another technique for reducing the amount of form image data, a technique for generating a differential image between a known form image where data is not written and an image of the form to which data has been written, and for recording the differential image data with a recording device is known.
Additionally, a technique for reducing the amount of information of a differential image generated as described above is known. With this technique, a character region and other regions in a script image of an electronic document are initially identified. Next, a character region and other regions of an image superposed by being handwritten on the electronic document are identified. Then, the amount of displacement between each of the regions in the script image and each of the regions in the handwritten superposed image is detected, and a differential process is executed by correcting a corresponding position based on the detected amount of displacement, thereby preventing the differential process from being incomplete. However, this technique is a technique of merely recording only handwriting, and is not suitable for the usage of handling recorded data as trail information that is needed to guarantee the originality of the image. Moreover, this technique needs complicated process steps of initially identifying a character region and other regions of two images in order to reduce the amount of differential image data, of obtaining the amount of displacement of the two images based on identification results, and of generating a differential image after aligning the images.
In addition, a form management technique is known. With this technique, a print medium on which an image of a selected form and a barcode indicating a storage position name are printed is output when the name of the form is selected, and the image of the form is stored in the storage position indicated by the barcode when the image to which data has been written is input to the print medium.
Furthermore, a form creation technique is known. With this technique, a form ID of a created form is generated from a template ID created from a form template, and a form data ID created from overlaying form data, and a form template and form data of the created form are managed to be identifiable.
Techniques referred to in the following documents are known.
Document 1:
    Japanese Laid-open Patent Publication No. H11-175701Document 2:    Japanese Laid-open Patent Publication No. 2004-287682Document 3:    Japanese Laid-open Patent Publication No. H10-162087Document 4:    Japanese Laid-open Patent Publication No. 2009-110387